Reference electrode

ABSTRACT

A marine cathodic protection device for aluminum hulls, stern drives and outboard motors, adapted for through hull installation on the bottom of a boat. Housings utilizing airfoil cross-section reduce drag and afford protection for the electrode surfaces.

United States Patent Anderson Dec. 10, 1974 [54] REFERENCE ELECTRODE2,934,484 4/1960 Anderson 204/196 3,272,731 9/1966 Hutchison et al204/196 [75] Inventor: m Anders, Fond du 3,278,408 10/1966 Leonard eta1. 204/195 P 3,445,369 5/1969 Porter et al. 204/195 P [73] AssigneezBrunswick Corporation Skokie In. 3,625,851 12/1971 Geld 204/195 F [22]Filed: Mar. 29, 1973 primary E T [21] APP] 345,869 Attorney, Agent, orFirmWil1iarn G. Lawler, Jr.

52 US. Cl 204/195 F, 204/196 [57] ABSTRACT 51 Int. Cl. G01n 27/30, C23f13/00 A marine cathodic Protection device for n m [58] Field of Search204/147, 196, 195 F, 195 P hulls, stern drives and outboard motors,adapted for through hull installation on the bottom of a boat. [56] Refee e Ci d Housings utilizing airfoil cross-section reduce drag and UNITEDSTATES PATENTS afford protection for the electrode surfaces.

2,910,420 10/1959 Preiser 204/196 3 Claims, 6 Drawing Figures 5 PATENTEQ352 I 01974 snmlor z REFERENCE ELECTRODE BACKGROUND OF THE INVENTIONWith the advent of aluminum hulled boats, aluminum stern drivepropulsion units, and larger outboards with sizable areas of aluminumcasing below the water, it has become increasingly important to provideadequate cathodic protection; particularly in salt, brackish or pollutedwaters. In addition, visits to crowded marinas where shore power isoften taken aboard makes cathodic protection a virtual necessity.

The basic concept of cathodic protection of vessels is not new, andvarious configurations of anodes and reference electrodes have beentried. For example, U.S. Pat. No. 3,117,070 to the inventor teaches abronze half-cell suitable for use on a steel hull, and the assigneehereof has marketed a cathodic protection device employing cylindricalelectrodes mounted through the transom of the boat.

One problem with the prior art devices which mounted through the transomwas that they were out of the water when the boat was running at highspeed. This resulted in significant loss of protection.

Another problem with prior art electrodes which were capable of beingmounted on the bottom of a boat was the wearing away of the activematerial on the anode with a resulting deterioration in theeffectiveness of the system.

Accordingly it is an objective of the invention to provide an anode anda reference electrode particularly suited for installation on the bottomof a boat.

It is a further objective of the invention to protect the anode andreference electrode from abrasive damage such as that encountered when aboat runs aground.

It is a still further objective of the invention to maximize theruggedness and reliability of the aforesaid electrodes by enclosing themwithin rugged corrosion and erosion resistant housings.

Another objective of the invention, consistent with the foregoing, is toreduce water drag on the electrodes through utilization of streamlinedhousings.

SUMMARY OF THE PRESENT INVENTION Basically the invention comprises areference electrode and a companion anode, each retained by a separatemounted housing of modified airfoil cross-section. The anode s platinumelectrode surface is exposed only abaft the point of maximum camber ofits housing, and the reference electrode is enclosed within a chamberopening to the surrounding water through a series of apertures. Meansfor mounting the housings upon the bottom of the boat are provided,including conduits to permit electrical connection of the anode andreference electrode to a control circuit.

Chief among the advantages of the invention is protection of theelectrodes while affording them maximum possible exposure to thesurrounding seawater, and at a minimum cost in drag. A further advantageof the invention is increased protective capacity of electrodes throughselective use of materials, again made possible by the configuration ofthe aforementioned housings. Lastly, the invention provides rugged andreliable electrodes at a cost consistent with their use on smallpleasure crafts.

Other objectives, advantages, and various further features of noveltyand invention will be pointed out or will occur to those skilled in theart from a reading of the following specification in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and lb are perspective viewsof an anode and reference electrode respectively of the invention.

FIGS. 2a and 2b are longitudinal cross-sectional views of an anode and areference electrode respectively of the invention.

FIGS. 3a and 3b are lateral cross-sectional views of the anode andreference electrode of FIG. 1 taken respectively along lines 3a3a and3b3b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates thesimilarities and the differences between an anode 1 of the invention anda reference electrode 2. The overall size and shape of the housings 3and 4 of the two units are substantially identical. The housings havebeen given a modified airfoil shape so that they offer minimumresistance to passage through the water in the direction of the arrowsin FIG. 1. To avoid erosion and corrosion the housings are preferablymade of an acetal polymer plastic such as Celenex. This material wasselected for its resistance to the environment created by theelectrolytic action at the electrodes.

The anode electrode 5 extends aft from a point slightly aft of themaximum height or camber of the anode housing 3, to a point just forwardof the trailing edge of the housing 3; so that it is protected fromdirect frontal contact with the fluid stream passing over the anode, andwith sand or other solid objects over which may come in contact with thebottom of the boat and the forward part of the housing.

As illustrated best in FIGS. la and 3a, the edges of the anode housing 3surrounding the anode electrode 5 are rounded so that they contact thesurface of that electrode at an oblique angle. This affords the anodemaximum effective contact with the water, while still permitting it tobe protectively inset from the surrounding surfaces of the anode housing3.

The housings l and 2 are both molded inseparably to an anodized aluminumhead fitting 10 which extends into the bottom of the boat. V-shapedfins11 extend laterally from the fitting 10 to assure continued alignment ofthe electrode housings 3 and 4 under operating conditions. An anodizedaluminum stud 12 is utilized to retain the housings 3 and 4 in placebeneath the bottom of the boat. The lower end of the stud 12 is threadedinto and epoxiedwithin the fitting l0, and the upper end is threaded forreception of a flanged nut which bears against the inner surface of thehull bottom. An O-ring seal 15 (FIGS. 2 and 3) seals the fitting 10 tothe hull to prevent leakage around the fitting l0 and the stud 12. Thisseal should be able to withstand static compression and a widetemperature variation, and be impervious to the effects of lube oil,gasoline, engine exhaust and salt water.

Referring to FIGS. 2a and 3a a wire lead 20 extends through a bore 21 inthe stud l2 and the head fitting 10 where it is soldered to a brasseyelet 22. The anode electrode 5 is preferably made of a substrate oftitanium, niobium or tantalum plated with platinum. The eyelet isutilized to facilitate electrical connection of the wire 20 to theelectrode 5. The assembly is then potted by molding it within thehousing 3 as illustrated in FIG. 2a. As the outer surface of the anodeelectrode 5 is the only surface exposed to the water, platinum platingmay be confined to this area.

Leakage of water through the interior of the anode 1 is eliminated bypotting the anode, its connecting wire 20 and the outer ends of the headfitting within the anode housing 3. A series of fingers 25 extendangularly from the fitting 10 into the plastic material forming thehousing 3 to assure a secure mating between the two. In addition topermanently securing the anode electrode 5 in place within the housing3, the potting of the electrical elements as described prevents anypossible leakage of water into the boat through the channel 21 in thestud 12.

Referring to FIGS. 2b and 3b, the housing 4 of the reference electrode 2comprises a base 30 which is molded to a head fitting 10. A coil 26,preferably a silver wire, is mounted within a channel 27 extendinglongitudinally through an upper portion of the housing base 30. Theelectrode wire coil should be sufficient size as to prevent surfacepolarization by the current it may be subjected to under operatingconditions. One end of the coil wire becomes an electrical lead 28 whichextends through a bore 29 drilled through the housing base 30 and thehead element 10 after the aforementioned molding thereof. Lead 28 issilver soldered to an electrical lead 40 from a control circuit at apoint within a cavity 31 in the head fitting 10. A suitable pottingcompound is then poured into the cavity 31 until the soldered junctionis completely covered, to protect it from any water which may enterthrough the bore 29 and also prevent any leakage of water into the boatthrough the interior of fitting It].

The reference electrode housing includes a separate cover 32 which ismolded separately and set in place as illustrated after installation ofthe reference electrode coil 26. A series of holes 33 may be molded ordrilled in the cover 32 to provide access for the seawater to come incontact with the reference electrode coil 26.

The wires 20 and 30 leading from the anode and reference electroderespectively may be connected to any appropriate cathodic controlcircuit, such as that presently incorporated in a cathodic protectiondevice sold by the assignee hereof under the trademark Mercathode.

While the principles of the invention have been described in connectionwith the above specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of the invention.

1 claim:

1. A reference electrode for a marine cathodic protection device,comprising:

a housing,

a wire electrode mounted in said housing, and means for mounting saidhousing to the hull of a boat, in cluding means providing for connectionof said wire electrode to a control circuit for the cathodic protectiondevice,

said housing comprising a body of erosion and corrosion resistantelectrically insulating material, said body being molded about ametallic structural support member including a first portion having aplurality of radially extending fins adapted to engage the hull of aboat for maintaining said support member on the hull in a preselectedrotational position, and a second portion having a plurality of fingersextending radially into the molded position of said body for maintainingsaid body in position on said support member,

said housing having a recess therein receiving said wire electrode, anda cover mounted over said recess, said body and cover having an air foilcamber along its longitudinal axis and said cover having a plurality ofpassages therethrough communicating with said recess.

2. The device of claim 1 wherein said structural member has a recesstherein, said mounting means further includes a threaded tubular membercommunicating with said recess and connected to said structuralsupporting member and adapted to extend through the hull of a boat toretain said reference electrode in preselected position upon the hull;and wherein said means for connection of said electrode to a controlcircuit includes a lead extending through said tubular member and intosaid recess, means connecting said lead to said electrode within saidrecess and a potting compound filling said recess around said connectionand sealing the connection of said body and tubular member against thepassage of water therethrough.

3. The device of claim 2 further including resilient means disposedadjacent said body and around said tu bular member and adapted forsealing engagement between said molded body and the hull of a boat.

1. A reference electrode for a marine cathodic protection device,comprising: a housing, a wire electrode mounted in said housing, andmeans for mounting said housing to the hull of a boat, including meansproviding for connection of said wire electrode to a control circuit forthe cathodic protection device, said housing comprising a body oferosion and corrosion resistant electrically insulating material, saidbody being molded about a metallic structural support member including afirst portion having a plurality of radially extending fins adapted toengage the hull of a boat for maintaining said support member on thehull in a preselected rotational position, and a second portion having aplurality of fingers extending radially into the molded position of saidbody for maintaining said body in position on said support member, saidhousing having a recess therein receiving said wire electrode, and acover mounted over said recess, said body and cover having an air foilcamber along its longitudinal axis and said cover having a plurality ofpassages therethrough communicating with said recess.
 2. The device ofclaim 1 wherein said structural member has a recess therein, saidmounting means further includes a threaded tubular member communicatingwith said recess and connected to said structural supporting member andadapted to extend through the hull of a boat to retain said referenceelectrode in preselected position upon the hull; and wherein said meansfor connection of said electrode to a control circuit includes a leadextending through said tubular member and into said recess, meansconnecting said lead to said electrode within said recess and a pottingcompound filling said recess around said connection and sealing theconnection of said body and tubular member against the passage of watertherethrough.
 3. The device of claim 2 further including resilient meAnsdisposed adjacent said body and around said tubular member and adaptedfor sealing engagement between said molded body and the hull of a boat.